Thiochroman and dihydrobenzothiophene herbicidal agents and methods of their preparation are described in U.S. Pat. No. 5,506,194, U.S. Pat. No. 5,607,898 and WO 97/08164 among other publications. The 6-(arylcarbonyl)thiochroman and 5-(arylcarbonyl)dihydrobenzothiophene derivatives are effective herbicidal agents at low rates of application and demonstrate selective control of noxious weeds in the presence of important economic crops such as corn and rice.
A common route to prepare these useful herbicidal agents entails the dehalogenation of an 8-halo-6-carbethoxythiochroman or 7-halo-5-carbethoxydihydrobenzothiophene intermediate compound. Heretofore, methods to dehalogenate said intermediate compound required high pressure hydrogenation techniques. Further, product yield and quality may be less than satisfactory. The importance of the dehalogenated 6-carbethoxythiochroman and 5-carbethoxydihydrobenzothiophene intermediates, particularly as key intermediates in the manufacture of herbicidal arylcarbonylthiochroman and arylcarbonyldihydro-benzothiophene agents, creates a significant need in the art for alternative and effective processes for their preparation.